Yet another UK heatwave on the way

By 15th July, 2026 had already recorded more days above 30°C than the whole of 1976. It also became the first year on record to reach 35°C in May. The UK's highest temperature of 40.3°C, set on 19th July 2022, is still standing, but the persistence of high levels of heat this summer has been astonishing. The hottest day so far was on 26th June, when 38°C was recorded at Lingwood, Norfolk.

With more heat on the way, could the hottest day of the year still be ahead? Whilst it's possible, the days are now shortening, giving less time for solar heating. The flipside of the coin is that the ground is baked in much of the southern half of the UK, so more of the solar input goes into warming the air above it rather than evaporating moisture. Also, sea temperatures around our shores are anomalously high. 

Overview of the likely heatwave

Temperatures will actually dip a little in the short term after peaking on Sunday 9th August, when 33°C could be reached in the south. Cooler air will be pushing southwards so on Monday maximums of around 27°C are likely in the south, while it will be cooler in the north.

However, high pressure will be building across the UK and slipping eastwards into continental Europe. This will lead to very warm air pushing northwards, particularly over southern, central and eastern areas. 

By Friday 14th August another area of high pressure is likely to begin building to the west of the UK and quickly become the dominant feature. Air flows in a clockwise direction around high pressure, so cooler air will start returning southwards. That means southern Britain can expect to hold on to the heat for the longest. This type of pattern lends uncertainty in terms of the timing of the transition and the potential for showery rain. A potent thundery breakdown isn't favoured, although it cannot be completely discounted. That scenario would be more likely if low pressure pushed up from the south or southwest. 

Is it just for the south?

No. The highest temperatures will be in southern and central areas, but the warmth is expected to extend northwards for a time. Temperatures in much of the northern half of the UK will probably peak in the mid-20s Celsius on Thursday 13th or Friday 14th. The main exceptions will likely be northern and western Scotland, where a cooling Atlantic influence remains. This also brings the potential for showers or longer spells of rain, which could spread into Northern Ireland too. 

How high could temperatures go?

Details will firm up closer to the time, but presently computer models are predicting that temperatures will peak in the mid-30°s Celsius. For example, the spread of forecasts for London from ensemble models ranges from about 30°C to 37°C, with the hottest day likely to be either the 13th or 14th of August. 

The data table above shows the maximum temperature forecasts for London, based on data from the GEFS ensemble. On Thursday 13th August 90% of the runs are predicting 30°C or higher, with 16% going for 35°C or higher. This falls to 58% and 3% respectively on the following day. It's worth remembering that: 

• London won't necessarily be the hottest location.
• The official reporting network is relatively sparse, so it's very possible that the highest temperature in the UK won't be captured; this of course is not unique to the coming period.

Could temperatures exceed the 37°C upper limit which the ensembles are currently showing for London? It's not out of the question. For example, the GFS model has the hottest conditions further north, affecting the East Midlands, Lincolnshire and South Yorkshire. If it is right, 38°C would be reached, so it's also possible that it could turn out to be the hottest day of the year. 

If 35°C is reached, August will be the fourth consecutive month to achieve this, something that has never been recorded before. In fact, the highest value reached in the whole of the 1980s was 34.4°C, at Mickleham, Surrey on 22nd July 1989. In the much-discussed summer of 1976 the peak was 35.9°C at Cheltenham, Gloucestershire on 3rd July.

How long will it last?

A transition to cooler conditions is being signalled from around 15th August. That said, the spread of outcomes widens again in the following days, and although the majority of models persist with the cooling trend, a minority show the heat returning yet again.

Even if somewhat cooler conditions do return quite quickly, the signal for widespread rain in the south remains very weak. In fact the ECMWF IFS model shows no measurable rain in much of southern Britain between Saturday 8th and Tuesday 18th August. The chart above illustrates the forecast totals for this period. 

As we've seen in recent years, the potential for hot conditions in southern and central areas of the UK can continue well into September. Therefore, it's highly possible this record-breaking summer could still have a few tricks left to play.